/*
 * Copyright (c) 2016-present, Yann Collet, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under both the BSD-style license (found in the
 * LICENSE file in the root directory of this source tree) and the GPLv2 (found
 * in the COPYING file in the root directory of this source tree).
 * You may select, at your option, one of the above-listed licenses.
 */

/* **************************************
 *  Compiler Warnings
 ****************************************/
#ifdef _MSC_VER
#pragma warning(disable : 4127) /* disable: C4127: conditional expression is constant */
#endif

/*-*************************************
 *  Includes
 ***************************************/
#include "dibio.h"

#include <assert.h>
#include <errno.h>  /* errno */
#include <stdio.h>  /* fprintf, fopen, ftello64 */
#include <stdlib.h> /* malloc, free */
#include <string.h> /* memset */

#include "error_private.h"
#include "mem.h"      /* read */
#include "platform.h" /* Large Files support */
#include "timefn.h"   /* UTIL_time_t, UTIL_clockSpanMicro, UTIL_getTime */
#include "util.h"     /* UTIL_getFileSize, UTIL_getTotalFileSize */

/*-*************************************
 *  Constants
 ***************************************/
#define KB *(1 << 10)
#define MB *(1 << 20)
#define GB *(1U << 30)

#define SAMPLESIZE_MAX (128 KB)
#define MEMMULT 11          /* rough estimation : memory cost to analyze 1 byte of sample */
#define COVER_MEMMULT 9     /* rough estimation : memory cost to analyze 1 byte of sample */
#define FASTCOVER_MEMMULT 1 /* rough estimation : memory cost to analyze 1 byte of sample */
static const size_t g_maxMemory = (sizeof(size_t) == 4) ? (2 GB - 64 MB) : ((size_t)(512 MB) << sizeof(size_t));

#define NOISELENGTH 32

/*-*************************************
 *  Console display
 ***************************************/
#define DISPLAY(...) fprintf(stderr, __VA_ARGS__)
#define DISPLAYLEVEL(l, ...)  \
    if (displayLevel >= l) {  \
        DISPLAY(__VA_ARGS__); \
    }

static const U64 g_refreshRate = SEC_TO_MICRO / 6;
static UTIL_time_t g_displayClock = UTIL_TIME_INITIALIZER;

#define DISPLAYUPDATE(l, ...)                                                                   \
    {                                                                                           \
        if (displayLevel >= l) {                                                                \
            if ((UTIL_clockSpanMicro(g_displayClock) > g_refreshRate) || (displayLevel >= 4)) { \
                g_displayClock = UTIL_getTime();                                                \
                DISPLAY(__VA_ARGS__);                                                           \
                if (displayLevel >= 4)                                                          \
                    fflush(stderr);                                                             \
            }                                                                                   \
        }                                                                                       \
    }

/*-*************************************
 *  Exceptions
 ***************************************/
#ifndef DEBUG
#define DEBUG 0
#endif
#define DEBUGOUTPUT(...) \
    if (DEBUG)           \
        DISPLAY(__VA_ARGS__);
#define EXM_THROW(error, ...)                                                 \
    {                                                                         \
        DEBUGOUTPUT("Error defined at %s, line %i : \n", __FILE__, __LINE__); \
        DISPLAY("Error %i : ", error);                                        \
        DISPLAY(__VA_ARGS__);                                                 \
        DISPLAY("\n");                                                        \
        exit(error);                                                          \
    }

/* ********************************************************
 *  Helper functions
 **********************************************************/
#undef MIN
#define MIN(a, b) ((a) < (b) ? (a) : (b))

/* ********************************************************
 *  File related operations
 **********************************************************/
/** DiB_loadFiles() :
 *  load samples from files listed in fileNamesTable into buffer.
 *  works even if buffer is too small to load all samples.
 *  Also provides the size of each sample into sampleSizes table
 *  which must be sized correctly, using DiB_fileStats().
 * @return : nb of samples effectively loaded into `buffer`
 * *bufferSizePtr is modified, it provides the amount data loaded within buffer.
 *  sampleSizes is filled with the size of each sample.
 */
static unsigned DiB_loadFiles(void* buffer,
                              size_t* bufferSizePtr,
                              size_t* sampleSizes,
                              unsigned sstSize,
                              const char** fileNamesTable,
                              unsigned nbFiles,
                              size_t targetChunkSize,
                              unsigned displayLevel) {
    char* const buff = (char*)buffer;
    size_t pos = 0;
    unsigned nbLoadedChunks = 0, fileIndex;

    for (fileIndex = 0; fileIndex < nbFiles; fileIndex++) {
        const char* const fileName = fileNamesTable[fileIndex];
        unsigned long long const fs64 = UTIL_getFileSize(fileName);
        unsigned long long remainingToLoad = (fs64 == UTIL_FILESIZE_UNKNOWN) ? 0 : fs64;
        U32 const nbChunks = targetChunkSize ? (U32)((fs64 + (targetChunkSize - 1)) / targetChunkSize) : 1;
        U64 const chunkSize = targetChunkSize ? MIN(targetChunkSize, fs64) : fs64;
        size_t const maxChunkSize = (size_t)MIN(chunkSize, SAMPLESIZE_MAX);
        U32 cnb;
        FILE* const f = fopen(fileName, "rb");
        if (f == NULL)
            EXM_THROW(10, "zstd: dictBuilder: %s %s ", fileName, strerror(errno));
        DISPLAYUPDATE(2, "Loading %s...       \r", fileName);
        for (cnb = 0; cnb < nbChunks; cnb++) {
            size_t const toLoad = (size_t)MIN(maxChunkSize, remainingToLoad);
            if (toLoad > *bufferSizePtr - pos)
                break;
            {
                size_t const readSize = fread(buff + pos, 1, toLoad, f);
                if (readSize != toLoad)
                    EXM_THROW(11, "Pb reading %s", fileName);
                pos += readSize;
                sampleSizes[nbLoadedChunks++] = toLoad;
                remainingToLoad -= targetChunkSize;
                if (nbLoadedChunks == sstSize) { /* no more space left in sampleSizes table */
                    fileIndex = nbFiles;         /* stop there */
                    break;
                }
                if (toLoad < targetChunkSize) {
                    fseek(f, (long)(targetChunkSize - toLoad), SEEK_CUR);
                }
            }
        }
        fclose(f);
    }
    DISPLAYLEVEL(2, "\r%79s\r", "");
    *bufferSizePtr = pos;
    DISPLAYLEVEL(4, "loaded : %u KB \n", (unsigned)(pos >> 10))
    return nbLoadedChunks;
}

#define DiB_rotl32(x, r) ((x << r) | (x >> (32 - r)))
static U32 DiB_rand(U32* src) {
    static const U32 prime1 = 2654435761U;
    static const U32 prime2 = 2246822519U;
    U32 rand32 = *src;
    rand32 *= prime1;
    rand32 ^= prime2;
    rand32 = DiB_rotl32(rand32, 13);
    *src = rand32;
    return rand32 >> 5;
}

/* DiB_shuffle() :
 * shuffle a table of file names in a semi-random way
 * It improves dictionary quality by reducing "locality" impact, so if sample set is very large,
 * it will load random elements from it, instead of just the first ones. */
static void DiB_shuffle(const char** fileNamesTable, unsigned nbFiles) {
    U32 seed = 0xFD2FB528;
    unsigned i;
    assert(nbFiles >= 1);
    for (i = nbFiles - 1; i > 0; --i) {
        unsigned const j = DiB_rand(&seed) % (i + 1);
        const char* const tmp = fileNamesTable[j];
        fileNamesTable[j] = fileNamesTable[i];
        fileNamesTable[i] = tmp;
    }
}

/*-********************************************************
 *  Dictionary training functions
 **********************************************************/
static size_t DiB_findMaxMem(unsigned long long requiredMem) {
    size_t const step = 8 MB;
    void* testmem = NULL;

    requiredMem = (((requiredMem >> 23) + 1) << 23);
    requiredMem += step;
    if (requiredMem > g_maxMemory)
        requiredMem = g_maxMemory;

    while (!testmem) {
        testmem = malloc((size_t)requiredMem);
        requiredMem -= step;
    }

    free(testmem);
    return (size_t)requiredMem;
}

static void DiB_fillNoise(void* buffer, size_t length) {
    unsigned const prime1 = 2654435761U;
    unsigned const prime2 = 2246822519U;
    unsigned acc = prime1;
    size_t p = 0;

    for (p = 0; p < length; p++) {
        acc *= prime2;
        ((unsigned char*)buffer)[p] = (unsigned char)(acc >> 21);
    }
}

static void DiB_saveDict(const char* dictFileName, const void* buff, size_t buffSize) {
    FILE* const f = fopen(dictFileName, "wb");
    if (f == NULL)
        EXM_THROW(3, "cannot open %s ", dictFileName);

    {
        size_t const n = fwrite(buff, 1, buffSize, f);
        if (n != buffSize)
            EXM_THROW(4, "%s : write error", dictFileName)
    }

    {
        size_t const n = (size_t)fclose(f);
        if (n != 0)
            EXM_THROW(5, "%s : flush error", dictFileName)
    }
}

typedef struct {
    U64 totalSizeToLoad;
    unsigned oneSampleTooLarge;
    unsigned nbSamples;
} fileStats;

/*! DiB_fileStats() :
 *  Given a list of files, and a chunkSize (0 == no chunk, whole files)
 *  provides the amount of data to be loaded and the resulting nb of samples.
 *  This is useful primarily for allocation purpose => sample buffer, and sample sizes table.
 */
static fileStats DiB_fileStats(const char** fileNamesTable, unsigned nbFiles, size_t chunkSize, unsigned displayLevel) {
    fileStats fs;
    unsigned n;
    memset(&fs, 0, sizeof(fs));
    for (n = 0; n < nbFiles; n++) {
        U64 const fileSize = UTIL_getFileSize(fileNamesTable[n]);
        U64 const srcSize = (fileSize == UTIL_FILESIZE_UNKNOWN) ? 0 : fileSize;
        U32 const nbSamples = (U32)(chunkSize ? (srcSize + (chunkSize - 1)) / chunkSize : 1);
        U64 const chunkToLoad = chunkSize ? MIN(chunkSize, srcSize) : srcSize;
        size_t const cappedChunkSize = (size_t)MIN(chunkToLoad, SAMPLESIZE_MAX);
        fs.totalSizeToLoad += cappedChunkSize * nbSamples;
        fs.oneSampleTooLarge |= (chunkSize > 2 * SAMPLESIZE_MAX);
        fs.nbSamples += nbSamples;
    }
    DISPLAYLEVEL(4, "Preparing to load : %u KB \n", (unsigned)(fs.totalSizeToLoad >> 10));
    return fs;
}

/*! ZDICT_trainFromBuffer_unsafe_legacy() :
    Strictly Internal use only !!
    Same as ZDICT_trainFromBuffer_legacy(), but does not control `samplesBuffer`.
    `samplesBuffer` must be followed by noisy guard band to avoid out-of-buffer reads.
    @return : size of dictionary stored into `dictBuffer` (<= `dictBufferCapacity`)
              or an error code.
*/
size_t ZDICT_trainFromBuffer_unsafe_legacy(void* dictBuffer,
                                           size_t dictBufferCapacity,
                                           const void* samplesBuffer,
                                           const size_t* samplesSizes,
                                           unsigned nbSamples,
                                           ZDICT_legacy_params_t parameters);

int DiB_trainFromFiles(const char* dictFileName,
                       unsigned maxDictSize,
                       const char** fileNamesTable,
                       unsigned nbFiles,
                       size_t chunkSize,
                       ZDICT_legacy_params_t* params,
                       ZDICT_cover_params_t* coverParams,
                       ZDICT_fastCover_params_t* fastCoverParams,
                       int optimize) {
    unsigned const displayLevel = params            ? params->zParams.notificationLevel
                                  : coverParams     ? coverParams->zParams.notificationLevel
                                  : fastCoverParams ? fastCoverParams->zParams.notificationLevel
                                                    : 0; /* should never happen */
    void* const dictBuffer = malloc(maxDictSize);
    fileStats const fs = DiB_fileStats(fileNamesTable, nbFiles, chunkSize, displayLevel);
    size_t* const sampleSizes = (size_t*)malloc(fs.nbSamples * sizeof(size_t));
    size_t const memMult = params ? MEMMULT : coverParams ? COVER_MEMMULT : FASTCOVER_MEMMULT;
    size_t const maxMem = DiB_findMaxMem(fs.totalSizeToLoad * memMult) / memMult;
    size_t loadedSize = (size_t)MIN((unsigned long long)maxMem, fs.totalSizeToLoad);
    void* const srcBuffer = malloc(loadedSize + NOISELENGTH);
    int result = 0;

    /* Checks */
    if ((!sampleSizes) || (!srcBuffer) || (!dictBuffer))
        EXM_THROW(12, "not enough memory for DiB_trainFiles"); /* should not happen */
    if (fs.oneSampleTooLarge) {
        DISPLAYLEVEL(2, "!  Warning : some sample(s) are very large \n");
        DISPLAYLEVEL(2, "!  Note that dictionary is only useful for small samples. \n");
        DISPLAYLEVEL(2, "!  As a consequence, only the first %u bytes of each sample are loaded \n", SAMPLESIZE_MAX);
    }
    if (fs.nbSamples < 5) {
        DISPLAYLEVEL(2, "!  Warning : nb of samples too low for proper processing ! \n");
        DISPLAYLEVEL(2, "!  Please provide _one file per sample_. \n");
        DISPLAYLEVEL(2, "!  Alternatively, split files into fixed-size blocks representative of samples, with -B# \n");
        EXM_THROW(14, "nb of samples too low"); /* we now clearly forbid this case */
    }
    if (fs.totalSizeToLoad < (unsigned long long)(8 * maxDictSize)) {
        DISPLAYLEVEL(2, "!  Warning : data size of samples too small for target dictionary size \n");
        DISPLAYLEVEL(2, "!  Samples should be about 100x larger than target dictionary size \n");
    }

    /* init */
    if (loadedSize < fs.totalSizeToLoad)
        DISPLAYLEVEL(1, "Not enough memory; training on %u MB only...\n", (unsigned)(loadedSize >> 20));

    /* Load input buffer */
    DISPLAYLEVEL(3, "Shuffling input files\n");
    DiB_shuffle(fileNamesTable, nbFiles);

    DiB_loadFiles(srcBuffer, &loadedSize, sampleSizes, fs.nbSamples, fileNamesTable, nbFiles, chunkSize, displayLevel);

    {
        size_t dictSize;
        if (params) {
            DiB_fillNoise((char*)srcBuffer + loadedSize, NOISELENGTH); /* guard band, for end of buffer condition */
            dictSize = ZDICT_trainFromBuffer_unsafe_legacy(dictBuffer,
                                                           maxDictSize,
                                                           srcBuffer,
                                                           sampleSizes,
                                                           fs.nbSamples,
                                                           *params);
        } else if (coverParams) {
            if (optimize) {
                dictSize = ZDICT_optimizeTrainFromBuffer_cover(dictBuffer,
                                                               maxDictSize,
                                                               srcBuffer,
                                                               sampleSizes,
                                                               fs.nbSamples,
                                                               coverParams);
                if (!ZDICT_isError(dictSize)) {
                    unsigned splitPercentage = (unsigned)(coverParams->splitPoint * 100);
                    DISPLAYLEVEL(2,
                                 "k=%u\nd=%u\nsteps=%u\nsplit=%u\n",
                                 coverParams->k,
                                 coverParams->d,
                                 coverParams->steps,
                                 splitPercentage);
                }
            } else {
                dictSize = ZDICT_trainFromBuffer_cover(dictBuffer,
                                                       maxDictSize,
                                                       srcBuffer,
                                                       sampleSizes,
                                                       fs.nbSamples,
                                                       *coverParams);
            }
        } else {
            assert(fastCoverParams != NULL);
            if (optimize) {
                dictSize = ZDICT_optimizeTrainFromBuffer_fastCover(dictBuffer,
                                                                   maxDictSize,
                                                                   srcBuffer,
                                                                   sampleSizes,
                                                                   fs.nbSamples,
                                                                   fastCoverParams);
                if (!ZDICT_isError(dictSize)) {
                    unsigned splitPercentage = (unsigned)(fastCoverParams->splitPoint * 100);
                    DISPLAYLEVEL(2,
                                 "k=%u\nd=%u\nf=%u\nsteps=%u\nsplit=%u\naccel=%u\n",
                                 fastCoverParams->k,
                                 fastCoverParams->d,
                                 fastCoverParams->f,
                                 fastCoverParams->steps,
                                 splitPercentage,
                                 fastCoverParams->accel);
                }
            } else {
                dictSize = ZDICT_trainFromBuffer_fastCover(dictBuffer,
                                                           maxDictSize,
                                                           srcBuffer,
                                                           sampleSizes,
                                                           fs.nbSamples,
                                                           *fastCoverParams);
            }
        }
        if (ZDICT_isError(dictSize)) {
            DISPLAYLEVEL(1, "dictionary training failed : %s \n", ZDICT_getErrorName(dictSize)); /* should not happen */
            result = 1;
            goto _cleanup;
        }
        /* save dict */
        DISPLAYLEVEL(2, "Save dictionary of size %u into file %s \n", (unsigned)dictSize, dictFileName);
        DiB_saveDict(dictFileName, dictBuffer, dictSize);
    }

    /* clean up */
_cleanup:
    free(srcBuffer);
    free(sampleSizes);
    free(dictBuffer);
    return result;
}
